1. Field of the Invention
The present invention relates to a light emitting device and a semiconductor device in each of which semiconductor layers are stacked on a substrate, and a method of manufacturing the devices.
2. Description of the Related Art
At present, a semiconductor laser (laser diode: LD) is used in various apparatuses such as optical disk drive, laser beam printer, and copying machine. FIG. 1 shows an example of the configuration of a conventional semiconductor laser. In the semiconductor laser, an n-type cladding layer 113, an active layer 114, a first p-type cladding layer 115, an etching stop layer 116, a second p-type cladding layer 117, and a p-side contact layer 118 are sequentially stacked on a substrate 111. By forming the second p-type cladding layer 117 in a strip shape in correspondence with a current injection area in the active layer 114, the current is limited. On the surface opposite to the substrate 111 side, a projected portion 123 is formed in correspondence with the second p-type cladding layer 117.
In the conventional semiconductor laser shown in FIG. 1, however, since the projected portion 123 is formed on the surface in correspondence with the second p-type cladding layer 117, the number of times a tool comes into contact with the projected portion 123 and its peripheral area in a manufacturing process and the like is large. It causes a problem such that the projected portion 123 and its periphery, for example, the second p-type cladding layer 117 and the current injection area in the active layer 114 are vulnerable to damage. For example, in a case such that a semiconductor laser is formed and carried to a measuring device by using an adsorbent tool, despite of examinations of improving the shape of a tool, controlling absorbing power of the tool, and the like, the damage cannot be effectively prevented. Due to this, the characteristics deteriorate.
The invention has been achieved in consideration of the above problems and its object is to provide a light emitting device and a semiconductor device each having improved characteristics by preventing damage caused by contact of a tool, and a method of manufacturing the devices.
According to an aspect of the invention, there is provided a light emitting device in which semiconductor layers including an active layer are stacked on a substrate, wherein the active layer has a current injection area into which a current is injected, a projected portion is provided in correspondence with the current injection area on the surface opposite to the substrate, a projected protective portion is provided in correspondence with an area other than the current injection area, and the protective portion is projected so that its top face is flush with or higher than that of the projected portion.
According to the invention, there is also provided a light emitting device in which semiconductor layers including an active layer are stacked on a substrate, wherein the active layer has a current injection area into which a current is injected, the semiconductor layer has a projected portion for limiting current in correspondence with the current injection area, a protective portion is provided in correspondence with an area other than the current injection area on the surface opposite to the substrate, and the protective portion is projected so that its top face is flush with or higher than that of the area corresponding to the current injection area, in the surface opposite to the substrate.
According to the invention, there is also provided a semiconductor device in which semiconductor layers are stacked on a substrate, including a projected portion and a projected protective portion having a top face flush with or higher than that of the projected portion on the surface opposite to the substrate.
A method of manufacturing a light emitting device according to the invention includes: a step of growing semiconductor layers including an active layer on a substrate; a step of forming a projected portion for limiting current in correspondence with the current injection area in the active layer in the semiconductor layer, thereby forming a projected portion in correspondence with the projected portion for limiting current on the surface opposite to the substrate; and a step of forming a protective portion projected so that its top face is flush with or higher than that of the projected portion on the surface opposite to the substrate in correspondence an area other than the current injection area in the active layer.
Another method of manufacturing a light emitting device according to the invention includes: a step of growing semiconductor layers including an active layer on a substrate; a step of forming a projected portion for limiting current on the semiconductor layer in correspondence with a current injection area in the active layer; and a step of forming a protective portion on the surface opposite to the substrate in correspondence with the area other than the current injection area in the active layer so that the top face of the protective portion is flush with or higher than that of the area corresponding to the current injection area, in the surface opposite to the substrate.
Further another method of manufacturing a semiconductor device according to the invention includes: a step of growing semiconductor layers on a substrate; and a step of forming a projected portion and a protective portion projected so that its top face is flush with or higher than that of the projected portion on the surface opposite to the substrate.
In each of the light emitting device and the semiconductor device according to the invention, on the surface opposite to the substrate of the device, the projected protective portion of which top face is either flush with or higher than that of the projected portion is provided. Consequently, the number of times a tool comes into contact with the projected portion is reduced, thereby preventing the projected portion and its periphery from being damaged.
In another light emitting device according to the invention, on the surface opposite to the substrate of the device, the protective portion of which top face is either flush with or higher than that of the area in the surface corresponding to the current injection area is provided. Consequently, the number of times a tool comes into contact with the surface corresponding to the current injection area is reduced, thereby preventing the surface corresponding to the current injection area and its periphery from being damaged.
In each of the method of manufacturing the light emitting device and the method of manufacturing the semiconductor device according to the invention, on the surface opposite to the substrate of the device, the projected protective portion of which top face is either flush with or higher than that of the projected portion is formed.
In another method of manufacturing the light emitting device according to the invention, on the surface opposite to the substrate of the device, the protective portion of which top face is either flush with or higher than that of the area in the surface corresponding to the current injection area is formed.
Other and further objects, features and advantages of the invention will appear more fully from the following description.